September 16, 2008

Space Oddity: Scientists discover Earth lifeform that can survive the vacuum of space

Long story short: Called tardigrades, the small (less than 1mm long) invertebrates, pictured above and below, were sent aloft on the European Space Agency's Foton spacecraft in September, 2007, then exposed to the vacuum of space.

"After these animals had been brought back and rehydrated, scientists found no difference in their survival and reproduction rates compared with tardigrades that had stayed back at home," according to a September 11, 2008 Economist story, which follows.
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Hardygrades

In October China will send three more astronauts into space — and two of them will brave a trip outside their vehicle wearing China’s brand new space suit. A space suit is a complicated device; in essence a complete miniature world that supplies all the things you need to support life and to protect its occupant. Without it, a human trip into space would be very brief.

Most living things cannot survive in space, though a few hardy bacteria and some lichen can do so for a while. Now, however, an animal has been found that can venture outside without a space suit. Ingemar Jonsson at Kristianstad University in Sweden, and his colleagues, have managed to send tardigrades, a small invertebrate animal less than 1mm long, out into space and back again.

They managed this using the European Space Agency’s Foton spacecraft in September 2007. The researchers report in Current Biology that two species of tardigrade (there are about 1,000 of them), were able to survive in space.

They exposed some to the vacuum of space. After these animals had been brought back and rehydrated, scientists found no difference in their survival and reproduction rates compared with tardigrades that had stayed back at home. (Although, presumably, the space travellers had a good yarn to tell their friends.)

The tardigrades found it harder to cope with solar radiation. Over 100 tardigrades were sent on the mission. But only three individuals of Milnesium tardigradum managed to survive, briefly, when exposed to vacuum plus the full range of ultraviolet radiation. But 12% survived, and went on to reproduce, when exposed only to less damaging UVA and UVB light.

The authors say that it is a mystery how these animals were capable of being revived after receiving such high doses of radiation under space conditions. Part of the answer could be that tardigrades have a unique metabolism which allows them to enter a state of suspended animation. They can survive long droughts on Earth in a dried-out state. Their survival methods might also involve an efficient mechanism for repairing damaged DNA, something that scientists are keen to learn more about.

Being able to withstand desiccation, starvation and extremes of temperature, has contributed towards the earthly success of the tardigrade, which live in habitats from damp moss to flowering plants, sand, freshwater and the ocean. More broadly, such hardiness leads to a question about whether tiny life forms may be able to hitchhike around the galaxy on meteorites — or even spacecraft. It is said that the meek will inherit the Earth. Perhaps the tardigrades will inherit the universe.
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Now let's move on to the Current Biology paper cited above; the abstract follows.
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Tardigrades survive exposure to space in low Earth orbit

Vacuum (imposing extreme dehydration) and solar/galactic cosmic radiation prevent survival of most organisms in space. Only anhydrobiotic organisms, which have evolved adaptations to survive more or less complete desiccation, have a potential to survive space vacuum, and few organisms can stand the unfiltered solar radiation in space. Tardigrades, commonly known as water-bears, are among the most desiccation and radiation-tolerant animals and have been shown to survive extreme levels of ionizing radiation. Here, we show that tardigrades are also able to survive space vacuum without loss in survival, and that some specimens even recovered after combined exposure to space vacuum and solar radiation. These results add the first animal to the exclusive and short list of organisms that have survived such exposure.
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